The present invention relates to a developing apparatus for use in an image forming apparatus such as an electrophotographic copier.
It is known that, in a developing apparatus, toner is supplied from a toner cartridge inserted into the apparatus and slidably attached on the upper surface of a developer case.
A toner supply outlet is formed in the bottom surface of the toner cartridge and a toner supply inlet is formed in the upper surface of the developer case. The toner supply outlet is opened and closed by a first shutter slidably attached to the bottom surface of the toner cartridge, whereas the toner supply inlet is opened and closed by a second shutter slidably attached to the upper surface of the developer case. Springs are provided to push the first and second shutters to close the toner supply outlet and inlet, respectively.
When the toner cartridge is loaded into the developer case along the upper surface, the first and second shutters are pushed against spring tension to release the toner supply outlet and inlet, respectively. Conversely, when the toner cartridge is unloaded from the developer case, the first and second shutters are pushed by spring tension to shut the toner supply outlet and inlet.
On the other hand, the toner cartridge houses a stirrer paddle for rotating and stirring toner to prevent coagulation. The developer case houses a toner supply auger in the developer case for transferring toner to a transfer mixer. The developer case further houses a transfer mixer, a concentration sensor, and a developing roller. The toner supplied by the toner supply auger is blended with carrier and transferred by the transfer mixer. The concentration of toner in the developing agent is detected by the concentration sensor.
When the concentration sensor detects that the toner concentration is equal to and lower than a predetermined value, the stirrer paddle initiates rotation to transfer toner. The toner is supplied from the toner supply outlet of the toner cartridge and introduced into the developer case through the toner supply inlet. The introduced toner in the developer case is transferred while being rotated by the supply auger and sent to the transfer mixer. The toner supply operation is continued until the concentration of toner (checked by the concentration sensor) reaches a predetermined value. The supplied toner is then transferred to the developing roller while being rotated by the transfer mixer.
The toner cartridge 2 must be exchanged when the toner cartridge 2 is empty or nearly empty as a result of toner being continuously supplied. Sometimes, however, the toner cartridge 2 must be exchanged even though it is not empty, for example, when the developing unit 1 is exchanged since the developing agent has ceased function, and when the photoconductive drum is exchanged since it has ceased function.
When toner completely runs out, toner leakage would not occur when the toner cartridge is exchanged since no toner is present in a toner supply passage from the toner cartridge to the supply auger.
However, when toner is contained in a toner cartridge, toner leaks since the toner supply passage is filled with toner. More specifically, when the toner cartridge is unloaded, the first and second shutters shut off the toner supply passage. Therefore, toner corresponding to at least the thickness of the shutters leaks out.
In an attempt to prevent toner from being scattered, a sealing material is usually attached to the shutter to tighten the shutter. With this, the thickness of the shutter tends to increase.
In most cases, the user performs the loading and unloading operation of a toner cartridge. However, even if toner leaks during the unload operation, the user rarely removes toner, unlike a service engineer. Therefore, the leaked toner attaches to electrically charged wire and to an optical lens, causing nonuniform electrification and bringing an adverse effect upon copy images, respectively.
The present invention has been attained in consideration of the aforementioned problems. An object of the present invention is to provide a developing apparatus causing no toner leakage even if a toner cartridge is exchanged while containing toner in it.
According to the present invention, there is provided a developing apparatus comprising
a developer case comprising a transfer mixer for mixing and stirring toner and carrier and transferring a toner-and-carrier mixture, a developing roller for supplying the toner transferred by the transfer mixer to an object to be developed, and a developer case having a toner supply inlet for introducing the toner;
a toner supply cartridge detachably attached to the developer case and having a toner supply outlet for supplying toner, toner being supplied from the toner supply outlet to the developer case through the toner supply inlet;
a toner supply auger slidably attached within the developer case along a shaft for transferring the toner supplied from the toner supply inlet along the shaft and sent to the transfer mixer;
an open-and-shut device for opening and closing the toner supply outlet and the toner supply inlet in accordance with loading and unloading of the toner supply cartridge; and
tension-applying means for moving the toner supply auger in an unloading direction of the toner supply cartridge when the toner supply cartridge is unloaded, thereby changing a site of the toner supply auger facing the toner supply inlet to another site of the toner supply auger close to its back end.
According to the present invention, there is provided a developing apparatus comprising
a developer case comprising a transfer mixer for mixing and stirring toner and carrier and transferring a toner-and-carrier mixture, a developing roller for supplying the toner transferred by the transfer mixer to an object to be developed, and a developer case having a toner supply inlet for introducing the toner;
a toner supply cartridge detachably attached to the developer case and having a toner supply outlet for supplying toner, toner being supplied from the toner supply outlet to the developer case through the toner supply inlet;
a toner supply auger slidably attached within the developer case along a shaft for transferring the toner supplied from the toner supply inlet along the shaft and sent to the transfer mixer;
an open-and-shut device for opening and closing the toner supply outlet and the toner supply inlet in accordance with loading and unloading of the toner supply cartridge,
wherein the open-and-shut device comprises a first shutter for opening and closing the toner supply outlet and a second shutter for opening and closing the toner supply inlet, and the second shutter has a communication hole for communicating the toner supply outlet and the toner supply inlet, and width of the toner supply outlet, communication hole, and toner supply inlet increase in this order in a cartridge loading and unloading direction.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.